1. The problem statement, all variables and given/known data Two threads, both having linear density μ1 and μ2 are connected and tensed with tension T. a) If traveling wave enters onto their junction, find ratios of amplitudes of reflected and input wave, transmitted and input wave, for μ2/μ1= 0, 1/4, 1, 4 and infinity b) Show that energy flow of input wave is equal to sum of reflected and transmitted wave. 3. The attempt at a solution As for part a, it is easy. We have three waves; Ψin = A cos (ωt - kz) ψTr = T*A cos (wt -k2z) ψRef = R*A cos (wt + kz) R= (Z1-Z2)/(Z1+Z2), T= 1+ R Z=(T0*μ)1/2 -> R=[(T0-μ1)1/2-(T0-μ2)1/2]/[(T0-μ1)1/2+(T0-μ2)1/2]=...=[(1-(μ2/μ1)1/2]/[(1+(μ2/μ1)1/2]. It is trivial to find those values now. As for part b) "The mean energy flux is , also written as and called I, the intensity. For a traveling wave, " quoted from (http://scienceworld.wolfram.com/physics/EnergyFlux.html) while i assume, U is potential energy. So basicly, I need to find flux for those three waves, and prove statement. How to find mean of U as for traveling waves?